This application claims the priority of German Patent Document DE 100 62 977.6, filed Dec. 16, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and apparatus for monitoring the interior space of a motor vehicle by means of infrared IR radiation.
The interior space of a motor vehicle is a highly dynamic space in terms of image processing technology. The effects of external light sources, such as the sun, are especially disruptive. The use of a Highly Dynamic Camera (HDR camera) is disadvantageous, in that such cameras are very slow and also very expensive. In depicting its data, the starting image of an HDR camera normally employs a depth of 16-20 bits (120 dB/1048 k gray scale values) per image point (pixel) in order to depict the full range of optical dynamics. This pixel depth is necessary for further processing of the image information, so that all relevant information can be derived from the initial scene. This translates into an increase in the amount of data per image relative to images from conventional monochromatic cameras, which generally depict the filmed scenery at 8 Bits per pixel (256 gray scale values/48 dB). This increased amount of data in turn results in a slower reading speed and increased consequential costs of the analyzing hardware. Both factors pose a considerable impediment to the use of HDR cameras in automotive applications.
The object of the invention is to create a method and apparatus of the type specified initially, with which it is possible to quickly and efficiently analyze a highly dynamic environment using an image processing procedure.
The invention meets the object with the following methods and apparatus.
In accordance with one aspect of the invention, a method for monitoring the interior space of a motor vehicle by means of IR radiation includes (1) placing at least one stationary IR transmitter and at least one stationary IR receiver for receiving reflected IR radiation in a central position in the vehicle interior space, (2) temporarily irradiating the vehicle interior space, (3) recording two images of the interior space at different illumination levels, and (4) subtracting the two images from one another with respect to their gray scale values for suppression of interfering effects.
In accordance with another aspect of the invention, an apparatus for monitoring an interior space of a motor vehicle by means of IR radiation includes an IR transmitter disposed in the vehicle interior space, an IR receiver for obtaining IR images of the interior space of the vehicle, and an analyzer for analyzing a signal received from the IR receiver. The IR transmitter is capable of emitting IR radiation at two different illumination levels to illuminate the interior space of the vehicle. The IR receiver is disposed in the vehicle interior space. The analyzer is designed to obtain an image of the interior space by subtracting gray scale values of one of the images from gray scale values of the other image, thereby suppressing interfering effects from external IR radiation sources. The two images are recorded at different illumination levels and at different instances of time.
In accordance with a further aspect of the invention, a method for monitoring an interior space of a motor vehicle by means of IR radiation includes (1) recording two images of the vehicle interior space at different illumination levels of IR radiation at different instances of time, and (2) obtaining an image of the interior space of the vehicle by subtracting gray scale values of one of the images from gray scale values of the other image, thereby suppressing interfering effects from external IR radiation sources on the image of the interior space. The IR radiation is emitted by an IR transmitter disposed in the interior space of the vehicle.
The capabilities of the camera are not expanded in this invention. Instead, the environment that is to be analyzed is influenced. This is achieved with innovative illumination methods, which are described in detail in the following.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.